Liquid contacting of post-quench effluent vapor streams from oxygenate to olefins conversion to capture catalyst fines

ABSTRACT

A process is provided for converting oxygenate to olefins from a fluidized bed reactor which comprises removal of catalyst fines from a quenched vaporous effluent by contacting with a liquid low in catalyst fines content, e.g., oxygenate feedstock, or by-product water from the oxygenates to olefins conversion which is stripped and/or filtered. The process typically comprises: contacting a feedstock comprising oxygenate with a catalyst comprising a molecular sieve under conditions effective to produce a deactivated catalyst having carbonaceous deposits and a product comprising the olefins; separating the deactivated catalyst from the product to provide a separated vaporous product which contains catalyst fines; quenching the separated vaporous product with a liquid medium containing water and catalyst fines, in an amount sufficient for forming a light product fraction comprising light olefins and catalyst fines and a heavy product fraction comprising water, heavier hydrocarbons and catalyst fines; treating the light product fraction by contacting with a liquid substantially free of catalyst fines to provide a light product fraction having reduced catalyst fines content and a liquid fraction of increased fines content; compressing the light product fraction having reduced catalyst fines content; and recovering the light olefins from the compressed light product fraction.

FIELD

The present invention relates to treatment of product streams fromprocesses utilizing fluidized catalyst, such as oxygenate-to-olefinprocesses (e.g., MTO), etc.

BACKGROUND

Olefins are traditionally produced from petroleum feedstocks bycatalytic or steam cracking processes. These cracking processes,especially steam cracking, produce light olefin(s), such as ethyleneand/or propylene, from a variety of hydrocarbon feedstocks. Ethylene andpropylene are important commodity petrochemicals useful in a variety ofprocesses for making plastics and other chemical compounds.

The petrochemical industry has known for some time that oxygenates,especially alcohols, are convertible into light olefin(s). There arenumerous technologies available for producing oxygenates includingfermentation or reaction of synthesis gas derived from natural gas,petroleum liquids or carbonaceous materials including coal, recycledplastics, municipal waste or any other organic material. Generally, theproduction of synthesis gas involves a combustion reaction of naturalgas, mostly methane, and an oxygen source into hydrogen, carbon monoxideand/or carbon dioxide. Other known syngas production processes includeconventional steam reforming, autothermal reforming, or a combinationthereof.

An important type of alternate feed for the production of light olefinsis oxygenate, such as, for example, alcohols, particularly methanol andethanol, dimethyl ether (DME), methyl ethyl ether, diethyl ether,dimethyl carbonate, and methyl formate. Many of these oxygenates may beproduced by fermentation, or from synthesis gas derived from naturalgas, petroleum liquids, carbonaceous materials, including coal, recycledplastics, municipal wastes, or any organic material. Because of the widevariety of sources, alcohol, alcohol derivatives, and other oxygenateshave promise as an economical, non-petroleum source for light olefinproduction. Methanol, the preferred alcohol for light olefin production,is typically synthesized from the catalytic reaction of hydrogen, carbonmonoxide and/or carbon dioxide in a methanol reactor in the presence ofa heterogeneous catalyst. For example, in one synthesis process methanolis produced using a copper/zinc oxide catalyst in a water-cooled tubularmethanol reactor. The preferred process for converting a feedstockcontaining methanol into one or more olefin(s), primarily ethyleneand/or propylene, involves contacting the feedstock with a catalystcomposition.

The catalysts used to promote the conversion of oxygenates to olefinsare molecular sieve catalysts. Because ethylene and propylene are themost sought after products of such a reaction, research has focused onwhat catalysts are most selective to ethylene and/or propylene, and onmethods for increasing the life and selectivity of the catalysts toethylene and/or propylene.

Catalytic processes utilizing fluidized bed technology for conversion ofhydrocarbon or oxygenates involving gas-solids contacting are widelyused in industry for productions of petroleum-based fuels, chemical feedstocks and other industrial materials. The gaseous reactants arecontacted with solid catalyst particles to provide gaseous products.Such processes often use continuous catalytic reactor unit operations,requiring catalyst regeneration at high temperature. FCC, MTO and otherprocesses usually employ oxidative regeneration to remove coke or othercarbonaceous deposits from spent or equilibrium catalysts. Theseoperations often utilize combustion air to burn carbonaceous matterdeposited on the catalyst during the conversion reactions. Ordinarily,this regeneration is carried out in a regeneration vessel separate fromthe main fluidized bed reactor. Attrition of the catalyst particles canoccur during circulation of the catalyst into smaller particles of, say,less than about 60 microns, in overall diameter, i.e., the largestparticle dimension.

The vaporous product from the reactor typically contains entrainedparticles such as catalyst fines carried from the process. Removal ofsuch particles is desirable inasmuch as these particles can causeerosion and plugging problems for downstream equipment, e.g., suctiondrums, compressors, pumps, valves, exchangers and piping. Ultimately,the particles may be vented with gases to ambient atmosphere fordisposal, e.g., through a cyclone used to separate solids from gases.Accordingly, it would be desirable to provide an economical method toreduce or substantially eliminate solids such as catalyst fines from theproduct effluent at a point upstream of equipment that can be damaged bysuch solids.

U.S. Pat. No. 6,121,504 to Kuechler et al. discloses a process forconverting oxygenates to olefins with direct product quenching for heatrecovery and to improve heat integration.

U.S. Pat. Nos. 6,403,854 and 6,459,009 to Miller et al. disclose aprocess for converting oxygenate to light olefins with improved heatrecovery from reactor effluent streams and improved waste recovery whichminimizes overall utility requirements. The reactor effluent is quenchedwith an aqueous stream in a two-stage process to facilitate theseparation of hydrocarbon gases from any entrained catalyst fines, aswell as to remove water and any heavy by-products such as C₆+hydrocarbons. A portion of the waste water stream withdrawn from thebottom of the quench tower is recycled to the quench tower at a pointabove where the reactor effluent is introduced to the quench tower. Thereferences do not appear to teach the use of liquid streams that aresubstantially free of catalyst fines for treating reactor effluents.

All of the above references are incorporated herein by reference intheir entirety.

SUMMARY

In one aspect, the invention relates to a process for convertingoxygenate to olefins which comprises: contacting a feedstock comprisingoxygenate with a catalyst comprising a molecular sieve under conditionseffective to produce a deactivated catalyst having carbonaceous depositsand a product comprising the olefins; separating the deactivatedcatalyst from the product to provide a separated vaporous product whichcontains catalyst fines; quenching the separated vaporous product with aliquid medium containing water and catalyst fines, in an amountsufficient for forming a light product fraction comprising light olefinsand catalyst fines and a heavy product fraction comprising water,heavier hydrocarbons and catalyst fines; treating the light productfraction by contacting with a liquid oxygenate substantially free ofcatalyst fines to provide a light product fraction having reducedcatalyst fines content and a liquid fraction of increased fines content;compressing the light product fraction having reduced catalyst finescontent; and recovering the light olefins from the compressed lightproduct fraction.

In one embodiment of this aspect of the invention, the liquid oxygenatesubstantially free of catalyst fines is selected from the groupconsisting of methanol and ethanol.

In another embodiment, the liquid oxygenate substantially free ofcatalyst fines is at least a portion of the feedstock comprisingoxygenate. The feedstock comprising oxygenate can be heated by thetreating.

In still another embodiment, the heated feedstock comprising oxygenateis contacted with the catalyst comprising a molecular sieve, i.e., theheated feedstock is cycled to a reactor wherein oxygenate is convertedto olefins.

In yet another embodiment, the liquid oxygenate substantially free ofcatalyst fines is by-product water from the contacting of the oxygenatewith the catalyst, which by-product water is condensed in a recoveryunit and treated to reduce catalyst fines content.

In still another embodiment, the liquid oxygenate substantially free ofcatalyst fines is taken from boiler feed water used to make steam.

In still yet another embodiment, the liquid medium containing water isderived from quench tower bottoms. The quench tower bottoms can bepassed through at least one of a quench heat exchange step and awater-methanol separation step before being cycled to the quench tower.

In yet another embodiment, the quenching takes place in a quench towerwherein the liquid medium containing water is introduced above where theseparated vaporous product is introduced, and the treating of the lightproduct fraction by contacting with a liquid oxygenate substantiallyfree of catalyst fines occurs within the quench tower above where theliquid medium containing water is introduced.

In yet still another embodiment, a liquid draw device is placed abovewhere the liquid medium containing water is introduced, from whichliquid draw device the liquid fraction of increased fines content istaken; and the liquid oxygenate substantially free of catalyst fines isintroduced at a point above the liquid draw device. Suitable liquid drawdevices for use in the present invention include draw trays or drawpans, such as chimney trays. A chimney tray typically consists of aflat, solid piece of metal connected to a standard downcomer andcontaining chimneys or vertically hollow structures that convey thevapors upward through the tray.

In another embodiment, a vapor-liquid contacting surface is placedbetween the liquid draw device and where the liquid oxygenatesubstantially free of catalyst fines is introduced. Any suitablevapor-liquid contacting surface can be used, e.g., one provided by atleast one material selected from the group consisting of random packing,structured packing and trays, as are well known to those of skill in theart.

In yet another embodiment, a demisting device is placed above where theliquid oxygenate substantially free of catalyst fines is introduced.

In still another embodiment, the quenching takes place in a quench towerwherein the liquid medium containing water is introduced above where theseparated vaporous product is introduced, and the treating of the lightproduct fraction occurs downstream of the quench tower.

In still yet another embodiment, the quenching takes place in a quenchtower and the treating of the light product fraction at least partiallyoccurs downstream in a suction drum.

In yet another embodiment, the quenching takes place in a quench towerand the treating of the light product fraction at least partially occursdownstream of the quench tower in a first stage suction drum. Typically,a vaporous effluent from the quench tower is directed to a suction drumintake from which liquid is removed below the intake and a vaporousoverhead taken from the top of the suction drum, which is directed tothe compressing step. The liquid oxygenate substantially free ofcatalyst fines is typically introduced to the suction drum above thesuction drum intake. The liquid oxygenate substantially free of catalystfines can be selected from the group consisting of methanol and ethanol.The liquid oxygenate substantially free of catalyst fines in oneembodiment is at least a portion of the feedstock comprising oxygenate.

In another embodiment, the liquid oxygenate substantially free ofcatalyst fines is by-product water from the contacting of the oxygenatewith the catalyst, which by-product water is condensed in a recoveryunit and treated to reduce catalyst fines content.

In still another embodiment, the liquid oxygenate substantially free ofcatalyst fines is boiler feed water used to make steam.

In yet another embodiment, a vapor-liquid contacting surface is placedbetween where the liquid oxygenate substantially free of catalyst finesis introduced to the suction drum and the suction drum intake. Thevapor-liquid contacting surface can be any suitable material providingsufficient surface area. Such vapor-liquid contacting surface can beprovided by at least one material selected from the group consisting ofrandom packing, structured packing and trays, which are well known tothose of skill in the art.

In one embodiment of this aspect of the present invention, the processutilizes a catalyst comprising molecular sieve selected from the groupconsisting of ALPO-18, ALPO-34, SAPO-17, SAPO-18, SAPO-34, and SAPO-44,as well as substituted groups thereof. The molecular sieve is preferablySAPO-34.

In another embodiment of this aspect of the invention, the liquid mediumcontaining water and catalyst fines contains at least about 0.01 wt %catalyst fines and the liquid oxygenate substantially free of catalystfines contains less than about 0.01 wt % catalyst fines.

In still another embodiment, the liquid medium containing water andcatalyst fines contains at least about 0.001 wt % catalyst fines and theliquid oxygenate substantially free of catalyst fines contains less thanabout 0.001 wt % catalyst fines.

In yet another embodiment, the liquid medium containing water andcatalyst fines contains at least about 0.0001 wt % catalyst fines, e.g.,at least about 0.00005 wt %, and the liquid oxygenate substantially freeof catalyst fines contains less than about 0.0001 wt % catalyst fines,e.g., less than about 0.00005 wt % catalyst fines.

In another aspect, the present invention relates to an apparatus forconverting oxygenates to olefins which comprises: a fluidized bedreactor for contacting a feedstock comprising oxygenate with a catalystcomprising a molecular sieve under conditions effective to produce adeactivated catalyst having carbonaceous deposits and a productcomprising the olefins; a separator for separating the deactivatedcatalyst from the product to provide a separated vaporous product whichcontains catalyst fines; a quench tower for quenching the separatedvaporous product with a liquid medium containing water and catalystfines, in an amount sufficient for forming a light product fractioncomprising light olefins and catalyst fines and a heavy product fractioncomprising water, heavier hydrocarbons and catalyst fines; a treater fortreating the light product fraction by contacting with a liquidoxygenate substantially free of catalyst fines to provide a lightproduct fraction having reduced catalyst fines content and a liquidfraction of increased fines content; a compressor for compressing thelight product fraction having reduced catalyst fines content; and arecovery train for recovering the light olefins from the compressedlight product fraction.

In one embodiment, the apparatus further comprises: a line to recycle atleast a portion of the liquid fraction of increased fines content to thereactor.

In another embodiment, the apparatus further comprises: a recovery unitfor condensing by-product water from the reactor and a treater to atleast partially remove catalyst fines from the condensed by-productwater.

In still another embodiment, the apparatus further comprises: a steamboiler having a source of boiler feed water which can also be used as asource of the liquid oxygenate substantially free of catalyst fines.

In yet another embodiment, the apparatus further comprises: a line torecycle at least a portion of the heavy product fraction comprisingwater, heavier hydrocarbons and catalyst fines to the quench tower asthe liquid medium containing water and catalyst fines. The line canfurther comprise at least one of a heat exchanger to remove heat fromthe heavy product fraction and a stripper to strip oxygenate from theheavy product fraction.

In still yet another embodiment, the quench tower of the apparatuscomprises in ascending order: an inlet for introducing the separatedvaporous product; an inlet for introducing the liquid medium containingwater; and the treater.

In another embodiment, the treater of the apparatus comprises a liquiddraw device having an outlet from which the liquid fraction of increasedfines content is taken; and the quench tower of the apparatus comprisesan inlet above the liquid draw device for introducing the liquidoxygenate substantially free of catalyst fines. The liquid draw devicecan be any suitable device known to those skilled in the art, e.g., achimney tray.

In yet another embodiment, the apparatus comprises a vapor-liquidcontacting surface placed between the liquid draw device and the inletfor introducing the liquid oxygenate substantially free of catalystfines. The vapor-liquid contacting surface is provided by any suitablematerial, e.g., at least one material selected from the group consistingof random packing, structured packing and trays.

In still another embodiment, the apparatus comprises a demisting deviceplaced above the inlet for introducing the liquid oxygenatesubstantially free of catalyst fines.

In still yet another embodiment, the apparatus comprises the treaterlocated downstream from the quench tower.

In another embodiment, the apparatus further comprises a suction drumlocated between the quench tower and the compressor.

In yet another embodiment, the suction drum of the apparatus comprises atreater for treating the light product fraction by contacting with aliquid oxygenate substantially free of catalyst fines to provide a lightproduct fraction having reduced catalyst fines content and a liquidfraction of increased fines content. The suction drum can be a firststage suction drum.

In still another embodiment, the suction drum of the apparatuscomprises: an intake for receiving vaporous effluent from the quenchtower; a lower outlet from which liquid is removed; and an overheadoutlet from which a vaporous overhead is taken for the compressor.

In still yet another embodiment, the suction drum of the apparatuscomprises an inlet for introducing the liquid oxygenate substantiallyfree of catalyst fines above the suction drum intake. The inlet forintroducing the liquid oxygenate substantially free of catalyst finescan be connected to a treater for reducing catalyst fines contentsupplied by a recovery unit that condenses by-product water taken fromthe reactor.

In another embodiment, the apparatus further comprises a boiler formaking steam and the inlet for introducing the liquid oxygenatesubstantially free of catalyst fines is connected to a source of boilerfeed water for the boiler.

In yet another embodiment, the apparatus further comprises avapor-liquid contacting surface placed between the inlet for introducingthe liquid oxygenate substantially free of catalyst fines to the suctiondrum and the suction drum intake. The vapor-liquid contacting surface isprovided by at least one material selected from the group consisting ofrandom packing, structured packing and trays.

DESCRIPTION OF THE DRAWINGS

The FIGURE is a schematic process flow diagram depicting certain aspectsof the invention.

DETAILED DESCRIPTION

Molecular Sieves and Catalysts Thereof for Use in OTO Conversion

Molecular sieves suited to use for converting oxygenates to olefins(OTO) have various chemical and physical, framework, characteristics.Molecular sieves have been well classified by the Structure Commissionof the International Zeolite Association according to the rules of theIUPAC Commission on Zeolite Nomenclature. A framework-type describes theconnectivity, topology, of the tetrahedrally coordinated atomsconstituting the framework, and making an abstraction of the specificproperties for those materials. Framework-type zeolite and zeolite-typemolecular sieves for which a structure has been established, areassigned a three letter code and are described in the Atlas of ZeoliteFramework Types, 5th edition, Elsevier, London, England (2001), which isherein fully incorporated by reference.

Non-limiting examples of these molecular sieves are the small poremolecular sieves of a framework-type selected from the group consistingof AEI, AFT, APC, ATN, ATT, ATV, AWW, BIK, CAS, CHA, CHI, DAC, DDR, EDI,ERI, GOO, KFI, LEV, LOV, LTA, MON, PAU, PHI, RHO, ROG, THO, andsubstituted forms thereof; the medium pore molecular sieves of aframework-type selected from the group consisting of AFO, AEL, EUO, HEU,FER, MEL, MFI, MTW, MTT, TON, and substituted forms thereof; and thelarge pore molecular sieves of a framework-type selected from the groupconsisting of EMT, FAU, and substituted forms thereof. Other molecularsieves have a framework-type selected from the group consisting of ANA,BEA, CFI, CLO, DON, GIS, LTL, MER, MOR, MWW and SOD. Non-limitingexamples of the preferred molecular sieves, particularly for convertingan oxygenate containing feedstock into olefin(s), include those having aframework-type selected from the group consisting of AEL, AFY, BEA, CHA,EDI, FAU, FER, GIS, LTA, LTL, MER, MFI, MOR, MTT, MWW, TAM and TON. Inone preferred embodiment, the molecular sieve of the invention has anAEI topology or a CHA topology, or a combination thereof, mostpreferably a CHA topology.

Molecular sieve materials all have 3-dimensional, four-connectedframework structure of corner-sharing TO₄ tetrahedra, where T is anytetrahedrally coordinated cation. These molecular sieves are typicallydescribed in terms of the size of the ring that defines a pore, wherethe size is based on the number of T atoms in the ring. Otherframework-type characteristics include the arrangement of rings thatform a cage, and when present, the dimension of channels, and the spacesbetween the cages. See van Bekkum, et al., Introduction to ZeoliteScience and Practice, Second Completely Revised and Expanded Edition,Volume 137, pages 1–67, Elsevier Science, B.V., Amsterdam, Netherlands(2001).

The small, medium and large pore molecular sieves have from a 4-ring toa 12-ring or greater framework-type. In a preferred embodiment, thezeolitic molecular sieves have 8-, 10- or 12-ring structures or largerand an average pore size in the range of from about 3 Å to 15 Å. In themost preferred embodiment, the molecular sieves utilized in theinvention, preferably silicoaluminophosphate molecular sieves have8-rings and an average pore size less than about 5 Å, preferably in therange of from 3 Å to about 5 Å, more preferably from 3 Å to about 4.5 Å,and most preferably from 3.5 Å to about 4.2 Å.

Molecular sieves, particularly zeolitic and zeolitic-type molecularsieves, preferably have a molecular framework of one, preferably two ormore corner-sharing [TO₄] tetrahedral units, more preferably, two ormore [SiO₄], [AlO₄] and/or [PO₄] tetrahedral units, and most preferably[SiO₄], [AlO₄] and [PO₄] tetrahedral units. These silicon, aluminum, andphosphorous based molecular sieves and metal containing silicon,aluminum and phosphorous based molecular sieves have been described indetail in numerous publications including for example, U.S. Pat. No.4,567,029 (MeAPO where Me is Mg, Mn, Zn, or Co), U.S. Pat. No. 4,440,871(SAPO), European Patent Application EP-A-0 159 624 (ELAPSO where El isAs, Be, B, Cr, Co, Ga, Ge, Fe, Li, Mg, Mn, Ti or Zn), U.S. Pat. No.4,554,143 (FeAPO), U.S. Pat. Nos. 4,822,478, 4,683,217, 4,744,885(FeAPSO), EP-A-0 158 975 and U.S. Pat. No. 4,935,216 (ZnAPSO, EP-A-0 161489 (CoAPSO), EP-A-0 158 976 (ELAPO, where EL is Co, Fe, Mg, Mn, Ti orZn), U.S. Pat. No. 4,310,440 (AlPO₄), EP-A-0 158 350 (SENAPSO), U.S.Pat. No. 4,973,460 (LiAPSO), U.S. Pat. No. 4,789,535 (LiAPO), U.S. Pat.No. 4,992,250 (GeAPSO), U.S. Pat. No. 4,888,167 (GeAPO), U.S. Pat. No.5,057,295 (BAPSO), U.S. Pat. No. 4,738,837 (CrAPSO), U.S. Pat. Nos.4,759,919, and 4,851,106 (CrAPO), U.S. Pat. Nos. 4,758,419, 4,882,038,5,434,326 and 5,478,787 (MgAPSO), U.S. Pat. No. 4,554,143 (FeAPO), U.S.Pat. No. 4,894,213 (AsAPSO), U.S. Pat. No. 4,913,888 (AsAPO), U.S. Pat.Nos. 4,686,092, 4,846,956 and 4,793,833 (MnAPSO), U.S. Pat. Nos.5,345,011 and 6,156,931 (MnAPO), U.S. Pat. No. 4,737,353 (BeAPSO), U.S.Pat. No. 4,940,570 (BeAPO), U.S. Pat. Nos. 4,801,309, 4,684,617 and4,880,520 (TiAPSO), U.S. Pat. Nos. 4,500,651, 4,551,236 and 4,605,492(TiAPO), U.S. Pat. Nos. 4,824,554, 4,744,970 (CoAPSO), U.S. Pat. No.4,735,806 (GaAPSO) EP-A-0 293 937 (QAPSO, where Q is framework oxideunit [QO₂]), as well as U.S. Pat. Nos. 4,567,029, 4,686,093, 4,781,814,4,793,984, 4,801,364, 4,853,197, 4,917,876, 4,952,384, 4,956,164,4,956,165, 4,973,785, 5,241,093, 5,493,066 and 5,675,050, all of whichare herein fully incorporated by reference.

Other molecular sieves include those described in EP-0 888 187 B1(microporous crystalline metallophosphates, SAPO₄ (UIO-6)), U.S. Pat.No. 6,004,898 (molecular sieve and an alkaline earth metal), U.S. patentapplication Ser. No. 09/511,943 filed Feb. 24, 2000 (integratedhydrocarbon co-catalyst), PCT WO 01/64340 published Sep. 7, 2001(thorium containing molecular sieve), and R. Szostak, Handbook ofMolecular Sieves, Van Nostrand Reinhold, New York, N.Y. (1992), whichare all herein fully incorporated by reference.

The more preferred silicon, aluminum and/or phosphorous containingmolecular sieves, and aluminum, phosphorous, and optionally silicon,containing molecular sieves include aluminophosphate (ALPO) molecularsieves and silicoaluminophosphate (SAPO) molecular sieves andsubstituted, preferably metal substituted, ALPO and SAPO molecularsieves. The most preferred molecular sieves are SAPO molecular sieves,and metal substituted SAPO molecular sieves. In an embodiment, the metalis an alkali metal of Group IA of the Periodic Table of Elements, analkaline earth metal of Group IIA of the Periodic Table of Elements, arare earth metal of Group IIIB, including the Lanthanides: lanthanum,cerium, praseodymium, neodymium, samarium, europium, gadolinium,terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium;and scandium or yttrium of the Periodic Table of Elements, a transitionmetal of Groups IVB, VB, VIB, VIIB, VIIIB, and IB of the Periodic Tableof Elements, or mixtures of any of these metal species. In one preferredembodiment, the metal is selected from the group consisting of Co, Cr,Cu, Fe, Ga, Ge, Mg, Mn, Ni, Sn, Ti, Zn and Zr, and mixtures thereof. Inanother preferred embodiment, these metal atoms discussed above areinserted into the framework of a molecular sieve through a tetrahedralunit, such as [MeO₂], and carry a net charge depending on the valencestate of the metal substituent. For example, in one embodiment, when themetal substituent has a valence state of +2, +3, +4, +5, or +6, the netcharge of the tetrahedral unit is between −2 and +2.

In one embodiment, the molecular sieve, as described in many of the U.S.patents mentioned above, is represented by the empirical formula, on ananhydrous basis:mR:(M_(x)Al_(y)P_(z))O₂wherein R represents at least one templating agent, preferably anorganic templating agent; m is the number of moles of R per mole of(M_(x)Al_(y)P_(z))O₂ and m has a value from 0 to 1, preferably 0 to 0.5,and most preferably from 0 to 0.3; x, y, and z represent the molefraction of Al, P and M as tetrahedral oxides, where M is a metalselected from one of Group IA, IIA, IB, IIIB, IVB, VB, VIIB, VIIB, VIIIBand Lanthanides of the Periodic Table of Elements, preferably M isselected from one of the group consisting of Co, Cr, Cu, Fe, Ga, Ge, Mg,Mn, Ni, Sn, Ti, Zn and Zr. In an embodiment, m is greater than or equalto 0.2, and x, y and z are greater than or equal to 0.01.

In another embodiment, m is greater than 0.1 to about 1, x is greaterthan 0 to about 0.25, y is in the range of from 0.4 to 0.5, and z is inthe range of from 0.25 to 0.5, more preferably m is from 0.15 to 0.7, xis from 0.01 to 0.2, y is from 0.4 to 0.5, and z is from 0.3 to 0.5.

Non-limiting examples of SAPO and ALPO molecular sieves of the inventioninclude one or a combination of SAPO-5, SAPO-8, SAPO-11, SAPO-16,SAPO-17, SAPO-18, SAPO-20, SAPO-31, SAPO-34, SAPO-35, SAPO-36, SAPO-37,SAPO-40, SAPO-41, SAPO-42, SAPO-44 (U.S. Pat. No. 6,162,415), SAPO-47,SAPO-56, ALPO-5, ALPO-11, ALPO-18, ALPO-31, ALPO-34, ALPO-36, ALPO-37,ALPO-46, and metal containing molecular sieves thereof. The morepreferred zeolite-type molecular sieves include one or a combination ofSAPO-18, SAPO-34, SAPO-35, SAPO-44, SAPO-56, ALPO-18 and ALPO-34, evenmore preferably one or a combination of SAPO-18, SAPO-34, ALPO-34 andALPO-18, and metal containing molecular sieves thereof, and mostpreferably one or a combination of SAPO-34 and ALPO-18, and metalcontaining molecular sieves thereof.

In an embodiment, the molecular sieve is an intergrowth material havingtwo or more distinct phases of crystalline structures within onemolecular sieve composition. In particular, intergrowth molecular sievesare described in the U.S. patent application Ser. No. 09/924,016 filedAug. 7, 2001 and PCT WO 98/15496 published Apr. 16, 1998, both of whichare herein fully incorporated by reference. In another embodiment, themolecular sieve comprises at least one intergrown phase of AEI and CHAframework-types. For example, SAPO-18, ALPO-18 and RUW-18 have an AEIframework-type, and SAPO-34 has a CHA framework-type.

The molecular sieves useful for oxygenates to olefins conversionprocesses are synthesized and then made or formulated into catalysts bycombining the synthesized molecular sieves with a binder and/or a matrixmaterial to form a molecular sieve catalyst composition. This molecularsieve catalyst composition is formed into useful shaped and sizedparticles by well-known techniques such as spray drying, pelletizing,extrusion, and the like.

Oxygenate to Olefins Process

In a preferred embodiment of an oxygenate to olefins process, thefeedstock contains one or more oxygenates, more specifically, one ormore organic compound(s) containing at least one oxygen atom. In themost preferred embodiment, the oxygenate in the feedstock is one or morealcohol(s), preferably aliphatic alcohol(s) where the aliphatic moietyof the alcohol(s) has from 1 to 20 carbon atoms, preferably from 1 to 10carbon atoms, and most preferably from 1 to 4 carbon atoms. The alcoholsuseful as feedstock in an oxygenate to olefins process include lowerstraight and branched chain aliphatic alcohols and their unsaturatedcounterparts.

Non-limiting examples of suitable oxygenates include methanol, ethanol,n-propanol, isopropanol, methyl ethyl ether, dimethyl ether, diethylether, di-isopropyl ether, formaldehyde, dimethyl carbonate, dimethylketone, acetic acid, and mixtures thereof.

In the most preferred embodiment, the feedstock is selected from one ormore of methanol, ethanol, dimethyl ether, diethyl ether or acombination thereof, more preferably methanol and dimethyl ether, andmost preferably methanol.

The various feedstocks discussed above, particularly a feedstockcontaining an oxygenate, more particularly a feedstock containing analcohol, is converted primarily into one or more olefin(s). Theolefin(s) or olefin monomer(s) produced from the feedstock typicallyhave from 2 to 30 carbon atoms, preferably 2 to 8 carbon atoms, morepreferably 2 to 6 carbon atoms, still more preferably 2 to 4 carbonsatoms, and most preferably ethylene and/or propylene.

Non-limiting examples of olefin monomer(s) include ethylene, propylene,butene-1, pentene-1,4-methyl-pentene-1, hexene-1, octene-1 and decene-1,preferably ethylene, propylene, butene-1, pentene-1,4-methyl-pentene-1,hexene-1, octene-1 and isomers thereof. Other olefin monomer(s) includeunsaturated monomers, diolefins having 4 to 18 carbon atoms, conjugatedor nonconjugated dienes, polyenes, vinyl monomers and cyclic olefins.

In the most preferred embodiment, the feedstock, preferably of one ormore oxygenates, is converted in the presence of a molecular sievecatalyst composition into olefin(s) having 2 to 6 carbons atoms,preferably 2 to 4 carbon atoms. Most preferably, the olefin(s), alone orin combination, are converted from a feedstock containing an oxygenate,preferably an alcohol, most preferably methanol, to the preferredolefin(s) ethylene and/or propylene.

There are many processes used to convert feedstock into olefin(s)including various cracking processes such as steam cracking, thermalregenerative cracking, fluidized bed cracking, fluid catalytic cracking,deep catalytic cracking, and visbreaking.

The most preferred process is generally referred to asmethanol-to-olefins (MTO). In a MTO process, typically an oxygenatedfeedstock, most preferably a methanol containing feedstock, is convertedin the presence of a molecular sieve catalyst composition into one ormore olefin(s), preferably and predominantly, ethylene and/or propylene,often referred to as light olefin(s).

In one embodiment of the process for conversion of a feedstock,preferably a feedstock containing one or more oxygenates, the amount ofolefin(s) produced based on the total weight of hydrocarbon produced isgreater than 50 weight percent, preferably greater than 60 weightpercent, more preferably greater than 70 weight percent, and mostpreferably greater than 85 weight percent.

Increasing the selectivity of preferred hydrocarbon products such asethylene and/or propylene from the conversion of an oxygenate using amolecular sieve catalyst composition is described in U.S. Pat. No.6,137,022 (linear velocity), and PCT WO 00/74848 published Dec. 14, 2000(methanol uptake index of at least 0.13), which are all herein fullyincorporated by reference.

The feedstock, in one embodiment, contains one or more diluent(s),typically used to reduce the concentration of the feedstock, and aregenerally non-reactive to the feedstock or molecular sieve catalystcomposition. Non-limiting examples of diluents include helium, argon,nitrogen, carbon monoxide, carbon dioxide, water, essentiallynon-reactive paraffins (especially alkanes such as methane, ethane, andpropane), essentially non-reactive aromatic compounds, and mixturesthereof. The most preferred diluents are water and nitrogen, with waterbeing particularly preferred.

The diluent, water, is used either in a liquid or a vapor form, or acombination thereof. The diluent is either added directly to a feedstockentering into a reactor or added directly into a reactor, or added witha molecular sieve catalyst composition. In one embodiment, the amount ofdiluent in the feedstock is in the range of from about 1 to about 99mole percent based on the total number of moles of the feedstock anddiluent, preferably from about 1 to 80 mole percent, more preferablyfrom about 5 to about 50, most preferably from about 5 to about 25. Inone embodiment, other hydrocarbons are added to a feedstock eitherdirectly or indirectly, and include olefin(s), paraffin(s), aromatic(s)(see, for example, U.S. Pat. No. 4,677,242, addition of aromatics) ormixtures thereof, preferably propylene, butylene, pentylene, and otherhydrocarbons having 4 or more carbon atoms, or mixtures thereof.

The process for converting a feedstock, especially a feedstockcontaining one or more oxygenates, in the presence of a molecular sievecatalyst composition, is carried out in a reaction process in a reactor,where the process is a fixed bed process, a fluidized bed process,preferably a continuous fluidized bed process, and most preferably acontinuous high velocity fluidized bed process.

The reaction processes can take place in a variety of catalytic reactorssuch as hybrid reactors that have a dense bed or fixed bed zones and/orfast fluidized bed reaction zones coupled together, circulatingfluidized bed reactors, riser reactors, and the like. Suitableconventional reactor types are described in, for example, U.S. Pat. No.4,076,796, U.S. Pat. No. 6,287,522 (dual riser), and FluidizationEngineering, D. Kunii and O. Levenspiel, Robert E. Krieger PublishingCompany, New York, N.Y. 1977, which are all herein fully incorporated byreference.

The preferred reactor types are riser reactors generally described inRiser Reactor, Fluidization and Fluid-Particle Systems, pages 48 to 59,F. A. Zenz and D. F. Othmer, Reinhold Publishing Corporation, New York,1960, and U.S. Pat. No. 6,166,282 (fast-fluidized bed reactor), and U.S.patent application Ser. No. 09/564,613, filed May 4, 2000 (multipleriser reactor), which are all herein fully incorporated by reference.

In a preferred embodiment, a fluidized bed process or high velocityfluidized bed process includes a reactor system, a regeneration systemand a recovery system.

The reactor system preferably is a fluid bed reactor system having afirst reaction zone within one or more riser reactor(s) within at leastone disengaging vessel, preferably comprising one or more cyclones. Inone embodiment, the one or more riser reactor(s) and disengaging vesselis contained within a single reactor vessel. Fresh feedstock, preferablycontaining one or more oxygenates, optionally with one or morediluent(s), is fed to the one or more riser reactor(s) in which azeolite or zeolite-type molecular sieve catalyst composition or cokedversion thereof is introduced. In one embodiment, the molecular sievecatalyst composition or coked version thereof is contacted with a liquidor gas, or combination thereof, prior to being introduced to the riserreactor(s), preferably the liquid is water or methanol.

Treatment of the oxygenate-containing feedstock prior to itsintroduction to the oxygenate to olefins conversion reactor may berequired to remove non-volatile contaminants.

The feedstock entering the reactor system is preferably converted,partially or fully, in the first reactor zone into a gaseous effluentthat enters the disengaging vessel along with a coked molecular sievecatalyst composition. In the preferred embodiment, cyclone(s) within thedisengaging vessel are designed to separate the molecular sieve catalystcomposition, preferably a coked molecular sieve catalyst composition,from the gaseous effluent containing one or more olefin(s) within thedisengaging zone. Cyclones are preferred, however, gravity effectswithin the disengaging vessel will also separate the catalystcompositions from the gaseous effluent. Other methods for separating thecatalyst compositions from the gaseous effluent include the use ofplates, caps, elbows, and the like.

In one embodiment of the disengaging system, the disengaging systemincludes a disengaging vessel, typically a lower portion of thedisengaging vessel is a stripping zone. In the stripping zone the cokedmolecular sieve catalyst composition is contacted with a gas, preferablyone or a combination of steam, methane, carbon dioxide, carbon monoxide,hydrogen, or an inert gas such as argon, preferably steam, to recoveradsorbed hydrocarbons from the coked molecular sieve catalystcomposition that is then introduced to the regeneration system. Inanother embodiment, the stripping zone is in a separate vessel from thedisengaging vessel and the gas is passed at a gas hourly superficialvelocity (GHSV) of from 1 hr⁻1 to about 20,000 hr⁻1 based on the volumeof gas to volume of coked molecular sieve catalyst composition,preferably at an elevated temperature from 250° C. to about 750° C.,preferably from about 350° C. to 650° C., over the coked molecular sievecatalyst composition.

The conversion temperature employed in the conversion process,specifically within the reactor system, is in the range of from about200° C. to about 1000° C., preferably from about 250° C. to about 800°C., more preferably from about 250° C. to about 750° C., yet morepreferably from about 300° C. to about 650° C., yet even more preferablyfrom about 350° C. to about 600° C. most preferably from about 350° C.to about 550° C.

The conversion pressure employed in the conversion process, specificallywithin the reactor system, varies over a wide range including autogenouspressure. The conversion pressure is based on the partial pressure ofthe feedstock exclusive of any diluent therein. Typically the conversionpressure employed in the process is in the range of from about 0.1 kPaato about 5 MPaa, preferably from about 5 kPaa to about 1 MPaa, and mostpreferably from about 20 kPaa to about 500 kPaa.

The weight hourly space velocity (WHSV), particularly in a process forconverting a feedstock containing one or more oxygenates in the presenceof a molecular sieve catalyst composition within a reaction zone, isdefined as the total weight of the feedstock excluding any diluents tothe reaction zone per hour per weight of molecular sieve in themolecular sieve catalyst composition in the reaction zone. The WHSV ismaintained at a level sufficient to keep the catalyst composition in afluidized state within a reactor.

Typically, the WHSV ranges from about 1 hr⁻¹ to about 5000 hr⁻¹,preferably from about 2 hr⁻¹ to about 3000 hr⁻¹, more preferably fromabout 5 hr⁻¹ to about 1500 hr⁻¹, and most preferably from about 10 hr⁻¹to about 1000 hr⁻¹. In one preferred embodiment, the WHSV is greaterthan 20 hr⁻¹, preferably the WHSV for conversion of a feedstockcontaining methanol and dimethyl ether is in the range of from about 20hr⁻¹ to about 300 hr^(−1.)

The superficial gas velocity (SGV) of the feedstock including diluentand reaction products within the reactor system is preferably sufficientto fluidize the molecular sieve catalyst composition within a reactionzone in the reactor. The SGV in the process, particularly within thereactor system, more particularly within the riser reactor(s), is atleast 0.1 meter per second (m/sec), preferably greater than 0.5 m/sec,more preferably greater than 1 m/sec, even more preferably greater than2 m/sec, yet even more preferably greater than 3 m/sec, and mostpreferably greater than 4 m/sec, e.g., greater than about 15 m/sec. See,for example, U.S. Pat. No. 6,552,240 to Lattner et al., which is hereinincorporated by reference.

In one preferred embodiment of the process for converting an oxygenateto olefin(s) using a silicoaluminophosphate molecular sieve catalystcomposition, the process is operated at a WHSV of at least 20 hr⁻¹ and aTemperature Corrected Normalized Methane Selectivity (TCNMS) of lessthan 0.016, preferably less than or equal to 0.01. See, for example,U.S. Pat. No. 5,952,538, which is herein fully incorporated byreference.

In another embodiment of the process for converting an oxygenate such asmethanol to one or more olefin(s) using a molecular sieve catalystcomposition, the WHSV is from 0.01 hr⁻¹ to about 100 hr⁻¹, at atemperature of from about 350° C. to 550° C., and silica to Me₂O₃ (Me isselected from Group 13 (IIIA), Groups 8, 9 and 10 (VIII) elements) fromthe Periodic Table of Elements), and a molar ratio of from 300 to 2500.See, for example, EP-0 642 485 B1, which is herein fully incorporated byreference.

Other processes for converting an oxygenate such as methanol to one ormore olefin(s) using a molecular sieve catalyst composition aredescribed in PCT WO 01/23500 published Apr. 5, 2001 (propane reductionat an average catalyst feedstock exposure of at least 1.0), which isherein incorporated by reference.

The coked molecular sieve catalyst composition is withdrawn from thedisengaging vessel, preferably by one or more cyclones(s), andintroduced to the regeneration system. The regeneration system comprisesa regenerator where the coked catalyst composition is contacted with aregeneration medium, preferably a gas containing oxygen, under generalregeneration conditions of temperature, pressure and residence time.

Non-limiting examples of the regeneration medium include one or more ofoxygen, O₃, SO₃, N₂O, NO, NO₂, N₂O₅, air, air diluted with nitrogen orcarbon dioxide, oxygen and water (U.S. Pat. No. 6,245,703), carbonmonoxide and/or hydrogen. The regeneration conditions are those capableof burning coke from the coked catalyst composition, preferably to alevel less than 0.5 weight percent based on the total weight of thecoked molecular sieve catalyst composition entering the regenerationsystem. The coked molecular sieve catalyst composition withdrawn fromthe regenerator forms a regenerated molecular sieve catalystcomposition.

The regeneration temperature is in the range of from about 200° C. toabout 1500° C., preferably from about 300° C. to about 1000° C., morepreferably from about 450° C. to about 750° C., and most preferably fromabout 550° C. to 700° C. The regeneration is in the range of from about10 psia (68 kPaa) to about 500 psia (3448 kPaa), preferably from about15 psia (103 kPaa) to about 250 psia (1724 kPaa), and more preferablyfrom about 20 psia (138 kPaa) to about 150 psia (1034 kPaa). Typically,the pressure is less than about 60 psia (414 kPaa).

The preferred residence time of the molecular sieve catalyst compositionin the regenerator is in the range of from about one minute to severalhours, most preferably about one minute to 100 minutes, and thepreferred volume of oxygen in the flue gas is in the range of from about0.01 mole percent to about 5 mole percent based on the total volume ofthe gas.

In one embodiment, regeneration promoters, typically metal containingcompounds such as platinum, palladium and the like, are added to theregenerator directly, or indirectly, for example with the coked catalystcomposition. Also, in another embodiment, a fresh molecular sievecatalyst composition is added to the regenerator containing aregeneration medium of oxygen and water as described in U.S. Pat. No.6,245,703, which is herein fully incorporated by reference.

In an embodiment, a portion of the coked molecular sieve catalystcomposition from the regenerator is returned directly to the one or moreriser reactor(s), or indirectly, by pre-contacting with the feedstock,or contacting with fresh molecular sieve catalyst composition, orcontacting with a regenerated molecular sieve catalyst composition or acooled regenerated molecular sieve catalyst composition described below.

The gaseous effluent from the OTO reactor is withdrawn from thedisengaging system and is passed through a recovery system. There aremany well-known recovery systems, techniques and sequences that areuseful in separating olefin(s) and purifying olefin(s) from the gaseouseffluent. Recovery systems generally comprise one or more or acombination of various separation, fractionation and/or distillationtowers, columns, splitters, or trains, for reaction systems such asethylbenzene manufacture (U.S. Pat. No. 5,476,978) and other derivativeprocesses such as aldehydes, ketones and ester manufacture (U.S. Pat.No. 5,675,041), and other associated equipment, for example, variouscondensers, heat exchangers, refrigeration systems or chill trains,compressors, knock-out drums or pots, pumps, and the like.

Non-limiting examples of these towers, columns, splitters or trains usedalone or in combination include one or more of a demethanizer,preferably a high temperature demethanizer, a deethanizer, adepropanizer, preferably a wet depropanizer, a wash tower often referredto as a caustic wash tower and/or quench tower, absorbers, adsorbers,membranes, ethylene (C₂) splitter, propylene (C₃) splitter, butene (C₄)splitter, and the like.

Various recovery systems useful for recovering predominately olefin(s),preferably prime or light olefin(s) such as ethylene, propylene and/orbutene are described in U.S. Pat. No. 5,960,643 (secondary rich ethylenestream), U.S. Pat. Nos. 5,019,143, 5,452,581 and 5,082,481 (membraneseparations), U.S. Pat. No. 5,672,197 (pressure dependent adsorbents),U.S. Pat. No. 6,069,288 (hydrogen removal), U.S. Pat. No. 5,904,880(recovered methanol to hydrogen and carbon dioxide in one step), U.S.Pat. No. 5,927,063 (recovered methanol to gas turbine power plant), andU.S. Pat. No. 6,121,504 (direct product quench), U.S. Pat. No. 6,121,503(high purity olefins without superfractionation), and U.S. Pat. No.6,293,998 (pressure swing adsorption), which are all herein fullyincorporated by reference.

The reaction products that are withdrawn from the OTO reactoradvantageously can be cooled and separated from water, a by-product ofthe conversion, in a quench tower before the olefin products arerecovered. In the quench tower, most of the water is condensed and thelight hydrocarbons and light oxygenates removed from the top of thequench tower as an overhead stream and the water removed from the bottomof the quench tower. Water removed from the quench tower comprises somedissolved light hydrocarbons and heavy by-products including heavyoxygenates, e.g., alcohols and ketones, which have a normal boilingpoint greater than or equal to water and which can be removed bystripping the water from heavy by-products with light gases such assteam or nitrogen. The feedstream passed to an OTO reactor can berefined methanol (essentially pure), or raw methanol comprising up toabout 30 weight percent water. The feedstream is advantageously heatedand vaporized prior to being charged to the fluidized bed OTO reactor,which requires a considerable amount of energy. Therefore, it isnecessary to recover as much as energy of the reactor effluent and useit to heat and vaporize the feedstream. However, water is substantiallythe only condensation product in the quench tower. The reaction zone cancomprise either a fixed bed or a fluidized reaction zone, but afluidized reaction zone is preferred.

In the operation of conventional quench systems, essentially all of thewater withdrawn from the bottom of the quench tower is contaminated andmust undergo further treatment before it can be returned to the processas pumparound. The pumparound can be cooled by indirect heat exchangewith the feedstream. Even after decontamination treatment, thepumparound or recycled water typically contains substantial amounts offines, which results in a quench tower overhead containing catalystfines in amounts deleterious to downstream installations, particularlysuction drums and compressors, e.g., the first stage suction drum andthe first stage compressor which are typically found in the recoverytrain.

The present invention treats quench overhead effluent streams byemploying a vapor-liquid contact zone upstream of these downstreaminstallations, particularly upstream of the first stage compressor,e.g., upstream of or at the first stage suction drum. In one embodimentthe treating takes place within the quench tower enclosure above wherethe quench water is introduced, i.e., the vapor-liquid contact zone ispositioned upstream of the introduction site for quench water.

The vapor-liquid contact zone employed within the quench tower enclosuretypically includes an optional liquid draw device such as a chimneytray, from which liquid such as water and/or oxygenate, e.g., methanol,can be drawn off. The drawn off liquid, if it contains water in excessto that permissible in an oxygenate feed to the reactor, can be passedto a water-methanol separation means, e.g., a stripper, as necessary.The liquid (after stripping if necessary) is passed to the oxygenate toolefins conversion reactor as feed (via a feed vaporizer as necessary).

Above the liquid draw device (or above or downstream of the quench waterinlet where no liquid draw device is used) can be placed suitablematerials providing solid surfaces for contacting the vaporous quenchoverhead effluent, e.g., trays or a packing material that facilitatesintimate gas/liquid contact. The gas/liquid contacting material mayinclude, but is not limited to random packing, structured packing and/ortrays. Examples of these include, Gauze, Ripple Trays, Sieve trays,cross-flow sieve, valve, or bubble cap trays, structured packings suchas Metal Max Pak® Mellapak®, Flexipac®, Gempak®, Goodloe®, Sulzer®, orrandom or dumped packing, such as berl saddles, Intalox® saddles,raschig rings, Pall® rings, and Nutter Rings™. These and other types ofsuitable gas/liquid contacting equipment are described in detail inKister, H. Z. Distillation Design, McGraw-Hill, N.Y. (1992), Chapters 6and 8, the disclosures of which are incorporated herein by reference.Typically such materials are packed to a depth ranging from about 2 ftto about 40 ft (from about 0.6 m to about 12 m), say, from about 4 ft toabout 20 ft (from about 1.2 m to about 6 m). A vapor-liquid contact zonecan be provided downstream of the quench tower enclosure in a separateenclosure upstream of the first stage compressor in the recovery train.Such a vapor-liquid contact zone can be provided in addition to the onein the quench tower enclosure, or alternately in place of thevapor-liquid contact zone in the quench tower enclosure. Typically, avapor-liquid contact zone downstream of the quench tower can be placedin a dedicated enclosure, or alternately within a suction drum.

A liquid substantially free of catalyst fines is introduced at a pointabove (or downstream of) the trays or packing materials in thevapor-liquid contact zone(s).

The overhead from the quench step, which typically contains at leastabout 0.0001 wt %, e.g., at least about 0.001 wt %, say, at least about0.01 wt %, e.g., from about 0.0001 to about 0.05 wt % of catalyst fineswhose overall particle diameter is less than about 60 microns, say, fromabout 5 to about 50 microns, e.g., from about 10 to about 30 microns,passes through a vapor-liquid contact zone. The vapor-liquid contactingzone comprises an inlet for introducing a liquid which is substantiallyfree of fines of overall diameter of less than about 60 microns, e.g.,from about 5 to about 50 microns, say, from about 10 to about 30microns. The liquid substantially free of catalyst fines contains aconcentration of catalyst fines lower than the overhead from the quenchstep, such that the vapor-liquid contacting provides a liquid fractionhaving increased catalyst fines content relative to the liquidsubstantially free of catalyst fines and an overhead or gaseous effluentfraction having decreased catalyst fines content relative to theoverhead from the quench step. The catalyst fines content of theoverhead from the quench step can vary depending on the efficiency ofupstream cyclones utilized, e.g., in the catalyst regenerator, as wellas upon the catalyst fines content of quench water recycled from thebottoms of the quench tower that contain catalyst fines. The finescontent can be dependent on the effectiveness of treatment, if any, ofthe bottoms prior to their reintroduction to the quench tower, as wellas the relative amounts of newly added quench water which is free ofcatalyst fines with recycled sources. Such treatments can include quenchwater separation treatment, e.g., water-methanol separation, e.g., in astripper.

The liquid substantially free of catalyst fines typically contains lessthan about 0.01 wt % catalyst fines (wherein the catalyst fines have anoverall diameter of less than about 60 microns, say, from about 5 toabout 50 microns), e.g., less than about 0.001 wt % catalyst fines, say,less than about 0.0001 wt % or even less than about 0.00001 wt % ofcatalyst fines, e.g., ranging from about 0.000005 wt % to about 0.005 wt% of catalyst fines. Such liquid can be obtained from any suitablesource providing a liquid of low or no catalyst fines content. Examplesinclude sources of oxygenate, e.g., methanol, and water or mixturesthereof which meet the catalyst fines content requirement either intheir original state or as treated to at least partially remove catalystfines. Suitable sources include the oxygenate feed for the oxygenate toolefins reactor, which may contain oxygenate alone or oxygenate, e.g.,methanol, mixed with water. Other sources include water obtained from astripper, which water has been filtered or otherwise treated to meet therequisite catalyst fines content. Sources of boiler feed water suitableas feed for steam boilers are also desirable sources of such liquidssubstantially free of catalyst fines, given their low or non-existentcatalyst fines content.

Such sources of liquid substantially free of catalyst fines can betreated to remove or add heat as necessary by heat exchange with otherstreams of the oxygenates to olefins conversion process or by any othersuitable means such as direct heating or cryogenic treatment, e.g., in aheat exchanger used to treat quench tower bottoms. Typically, the liquidsubstantially free of catalyst fines is cooler than the quench overheadit is used to treat, say, at least about 2° C., e.g., at least 10° C. oreven at least about 15° C. cooler, typically from about 2° to about 10°C. cooler. Temperatures of such liquid can range from about 2° to about8° C., e.g., from about 3° to about 5° C.

The present invention by providing additional treatment to quenchoverhead using liquid substantially free of catalyst fines, reduceserosion on downstream equipment while in certain instances providingadditional heat to oxygenate-containing feeds to the reactor.

Referring to the FIGURE, the method and apparatus of the presentinvention are depicted in a schematic process flow sheet. Regeneratorvessel 10, in which can be placed cyclones to at least partially removecatalyst fines, is operatively connected to reactor vessel 12 which isfed an oxygenated feed via line 14 which can be vaporized in feedvaporizer 15 prior to introduction to the reactor vessel 12 via line 16.Depleted catalyst is removed via line 17 to the regenerator 10 toregenerator catalyst inlet 18. Regenerated catalyst is taken from theregenerator via line 20 to the bottom of the reactor vessel 12. Vaporouscatalyst fines-containing product effluent is removed from the reactorvia line 22 and directly or indirectly (via heat exchanger 23 whichutilizes boiler feed water fed via line 24 to make steam taken from line25) introduced to quench tower 26 where it moves upwardly and contactsin a vapor-liquid contacting zone 27 a downwardly passing liquidcontaining water and catalyst fines introduced via line 28 which may befed by a stream derived from quench tower bottoms taken from line 30containing water, oxygenate, e.g., methanol and catalyst fines. Thestream from the quench tower bottoms can be optionally heat exchanged inheat exchanger 32 and optionally stripped, e.g., in a water-methanolseparator 34, prior to being directed to line 28. The quenched overheadwhich can contain problematic amounts of catalyst fines is passed to atreating zone where it undergoes additional vapor-liquid contacting in asecond vapor-liquid contacting zone at a point upstream of compressor68, this time with a liquid which is substantially free of catalystfines, providing a vaporous overhead of significantly reduced catalystfines content. In one embodiment, the vapor-liquid contacting zone ispresent in the enclosure of the quench tower itself. In this instancethe second vapor-liquid contacting zone includes a liquid draw devicesuch as chimney tray 36 wherein quench overhead passes via chimneyinlets and from which can be drawn off liquid collected in the tray vialine 38. The thus drawn off liquid contains catalyst fines taken fromthe quench tower overhead, and if containing water in excess of what issuitable for an oxygenate to olefins conversion reactor feed, can beconveyed to a stripper 40 (from which water is taken off via line 42)prior to being conveyed to feed vaporizer 15 and thence introduced tothe reactor vessel 12 via line 16.

Positioned above chimney tray 36 is a bed 39 providing surface area forvapor-liquid contacting, which bed can comprise trays or suitableirregular or regular packing as is known to those of skill in the art.Above the bed is an inlet for introducing liquid substantially free ofcatalyst fines via a liquid distributor 44 fed from line 46 which inturn can be fed by one or more suitable sources of liquid substantiallyfree of catalyst fines. Such sources include boiler feed water fed vialine 48, stripped water from an oxygenate-water stripper via line 50 orunvaporized oxygenate feed via line 52. The treated overhead from whichcatalyst fines have been removed by contacting with the liquidsubstantially free of catalyst fines passes out of a demister 54 locatedat the top of the quench tower enclosure which collects entrainedliquid. The quenched and treated overhead which contains low amounts ofcatalyst fines conveyed via line 56 to the recovery train which mayinclude an optional first stage suction drum 58 which removes anyadditional liquid formed in the quenched and treated overhead via line60 prior to a compression step. The overhead can be passed directly tothe compression step (if it has already passed to a post-quench treateras described above) or through a second (or third) vapor-liquidcontacting zone configured as described above with respect to the quenchtower enclosure except for lacking a chimney tray, liquid (and catalystfines) being drawn off via line 60. This vapor-liquid contacting zonecan be either a substitute for or, in addition to the vapor-liquidcontacting zone associated with the quench tower. The liquidsubstantially free of catalyst fines is introduced to the suction drum58 via line 64 which can be fed by any suitable source, including line46 which in turn is fed by any of lines 48, 50, and 52. Treated oruntreated overhead from the suction drum 58 is taken via line 66 whereit is directly or indirectly conveyed to a first stage compressor 68.The compressed overhead from the suction drum is conveyed via line 70 toa recovery train 72 providing recovered products via lines 74, 76, 78and 80.

While the present invention has been described and illustrated byreference to particular embodiments, those of ordinary skill in the artwill appreciate that the invention lends itself to variations notnecessarily illustrated herein. For this reason, then, reference shouldbe made solely to the appended claims for purposes of determining thetrue scope of the present invention.

1. A process for converting oxygenate to olefins which comprises:contacting a feedstock comprising oxygenate with a catalyst comprising amolecular sieve under conditions effective to produce a deactivatedcatalyst having carbonaceous deposits and a product comprising saidolefins; separating said deactivated catalyst from said product toprovide a separated vaporous product which contains catalyst fines;quenching said separated vaporous product with a liquid mediumcontaining water and catalyst fines, in an amount sufficient for forminga light product fraction comprising light olefins and catalyst fines anda heavy product fraction comprising water, heavier hydrocarbons andcatalyst fines; treating said light product fraction by contacting witha liquid oxygenate substantially free of catalyst fines to provide alight product fraction having reduced catalyst fines content and aliquid fraction of increased fines content, said liquid oxygenatesubstantially free of catalyst fines being selected from the groupconsisting of methanol and ethanol; compressing said light productfraction having reduced catalyst fines content; and recovering saidlight olefins from said compressed light product fraction.
 2. Theprocess of claim 1 wherein said liquid oxygenate substantially free ofcatalyst fines is methanol.
 3. The process of claim 1 wherein saidliquid oxygenate substantially free of catalyst fines is at least aportion of said feedstock comprising oxygenate.
 4. The process of claim3 wherein said feedstock comprising oxygenate is heated by saidtreating.
 5. The process of claim 4 wherein said heated feedstockcomprising oxygenate is contacted with said catalyst comprising amolecular sieve.
 6. The process of claim 1 wherein said liquid oxygenatesubstantially free of catalyst fines is contained in by-product waterfrom said contacting of the oxygenate with said catalyst, whichby-product water is condensed in a recovery unit and treated to reducecatalyst fines content.
 7. The process of claim 1 wherein said oxygenatecomprises methanol.
 8. The process of claim 1 wherein said liquid mediumcontaining water is derived from quench tower bottoms.
 9. The process ofclaim 8 wherein said quench tower bottoms are passed through at leastone of a quench heat exchange step and a water-methanol separation stepbefore being cycled to said quench tower.
 10. The process of claim 1wherein said quenching takes place in a quench tower wherein said liquidmedium containing water is introduced above where said separatedvaporous product is introduced, and said treating of said light productfraction by contacting with a liquid oxygenate substantially free ofcatalyst fines occurs within the quench tower above where said liquidmedium containing water is introduced.
 11. The process of claim 10wherein a liquid draw device is placed above where the liquid mediumcontaining water is introduced, from which liquid draw device saidliquid fraction of increased fines content is taken; and said liquidoxygenate substantially free of catalyst fines is introduced at a pointabove said liquid draw device.
 12. The process of claim 10 wherein saidliquid draw device is a chimney tray.
 13. The process of claim 11wherein a vapor-liquid contacting surface is placed between said liquiddraw device and where said liquid oxygenate substantially free ofcatalyst fines is introduced.
 14. The process of claim 13 wherein saidvapor-liquid contacting surface is provided by at least one materialselected from the group consisting of random packing, structured packingand trays.
 15. The process of claim 14 wherein a demisting device isplaced above where said liquid oxygenate substantially free of catalystfines is introduced.
 16. The process of claim 1 wherein said quenchingtakes place in a quench tower wherein said liquid medium containingwater is introduced above where said separated vaporous product isintroduced, and said treating of said light product fraction occursdownstream of said quench tower.
 17. The process of claim 1 wherein saidquenching takes place in a quench tower and said treating of said lightproduct fraction at least partially occurs downstream in a suction drum.18. The process of claim 1 wherein said quenching takes place in aquench tower and said treating of said light product fraction at leastpartially occurs downstream of said quench tower in a first stagesuction drum.
 19. The process of claim 17 wherein a vaporous effluentfrom said quench tower is directed to a suction drum intake from whichliquid is removed below said intake and a vaporous overhead taken fromthe top of said suction drum which is directed to said compressing step.20. The process of claim 19 wherein said liquid oxygenate substantiallyfree of catalyst fines is introduced to said suction drum above saidsuction drum intake.
 21. The process of claim 20 wherein said liquidoxygenate substantially free of catalyst fines is methanol.
 22. Theprocess of claim 20 wherein said liquid oxygenate substantially free ofcatalyst fines is at least a portion of said feedstock comprisingoxygenate.
 23. The process of claim 20 wherein said liquid oxygenatesubstantially free of catalyst fines is contained in by-product waterfrom said contacting of the oxygenate with said catalyst, whichby-product water is condensed in a recovery unit and treated to reducecatalyst fines content.
 24. The process of claim 20 wherein saidfeedstock comprising oxygenate comprises methanol.
 25. The process ofclaim 20 wherein a vapor-liquid contacting surface is placed betweenwhere said liquid oxygenate substantially free of catalyst fines isintroduced to said suction drum and said suction drum intake.
 26. Theprocess of claim 25 wherein said vapor-liquid contacting surface isprovided by at Least one material selected from the group consisting ofrandom packing, structured packing and trays.
 27. The process of claim 1wherein said molecular sieve is selected from the group consisting ofALPO-18, ALPO-34, SAPO-17, SAPO-18, SAPO-34, and SAPO-44 and substitutedgroups thereof.
 28. The process of claim 1 wherein said molecular sieveis SAPO-34.
 29. The process of claim 1 wherein said liquid mediumcontaining water and catalyst fines contains at least about 0.01 wt %catalyst fines and said liquid oxygenate substantially free of catalystfines contains less than about 0.01 wt % catalyst fines.
 30. The processof claim 1 wherein said liquid medium containing water and catalystfines contains at least about 0.001 wt % catalyst fines and said liquidoxygenate substantially free of catalyst fines contains less than about0.001 wt % catalyst fines.
 31. The process of claim 1 wherein saidliquid medium containing water and catalyst fines contains at leastabout 0.0001 wt % catalyst fines and said liquid oxygenate substantiallyfree of catalyst fines contains less than about 0.0001 wt % catalystfines.